Desalination: A National Perspective
NOTICE:
The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance.
Support for this study was provided by the U.S. Bureau of Reclamation under Grant No. 06CS811198. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided
support for the project.
Desalination: A National Perspective
NOTICE:
The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance.
Support for this study was provided by the U.S. Bureau of Reclamation under Grant No. 06CS811198. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided
support for the project.
Desalination & Water Purification Technologies
Introduction:
The world’s water consumption rate is doubling every 20 years, outpacing by two times the rate of population growth. The availability of good quality water is on the decline and water demand is on the rise. Worldwide availability of fresh water for industrial needs and human consumption is limited.
Various industrial and developmental activities in recent times have resulted in increasing the pollution level and deteriorating the water quality. Water shortages and unreliable water quality are considered major obstacles to achieve sustainable development and improvement in the quality of life. The water
demand in the country is increasing fast due to progressive increase in the demand of water for irrigation, rapid industrialization, and population growth and improving life standards. The existing water resources are diminishing (i) due to unequal distribution of rain water and occasional drought, (ii) excessive exploitation of ground water sources and its insufficient recharge, (iii) deterioration of water quality due to the discharge of domestic and industrial effluents without adequate treatment. This is resulting into water stress/ scarcity. Country is currently passing through social and economic transition.
The proportion of the population which is urban has doubled over the last thirty years (and is now about 30%), agriculture now accounts for about 25% of GDP and the economy has been growing at around 7-9% a year. Country has a highly seasonal pattern of rainfall, with 50% of precipitation falling
in just 15 days and over 90% of river flows in just four months
Desalination & Water Purification Technologies
Introduction:
The world’s water consumption rate is doubling every 20 years, outpacing by two times the rate of population growth. The availability of good quality water is on the decline and water demand is on the rise. Worldwide availability of fresh water for industrial needs and human consumption is limited.
Various industrial and developmental activities in recent times have resulted in increasing the pollution level and deteriorating the water quality. Water shortages and unreliable water quality are considered major obstacles to achieve sustainable development and improvement in the quality of life. The water
demand in the country is increasing fast due to progressive increase in the demand of water for irrigation, rapid industrialization, and population growth and improving life standards. The existing water resources are diminishing (i) due to unequal distribution of rain water and occasional drought, (ii) excessive exploitation of ground water sources and its insufficient recharge, (iii) deterioration of water quality due to the discharge of domestic and industrial effluents without adequate treatment. This is resulting into water stress/ scarcity. Country is currently passing through social and economic transition.
The proportion of the population which is urban has doubled over the last thirty years (and is now about 30%), agriculture now accounts for about 25% of GDP and the economy has been growing at around 7-9% a year. Country has a highly seasonal pattern of rainfall, with 50% of precipitation falling
in just 15 days and over 90% of river flows in just four months
Database Of Permitting Practices For Seawater Desalination Concentrate
Abstract:
The purpose of this research project was to identify the discharge information that permitting agencies need and the decision-making process they go through to permit discharge methods in order to help desalination project proponents focus and expedite their permitting efforts.
The project documented seawater reverse osmosis (SWRO) discharge regulatory issues and provided a critical overview of facility discharge-related information required for permitting desalination projects in the United States and selected countries with advanced environmental regulations and experience in implementing seawater desalination projects. Information was gathered from the three key U.S. states (California, Florida, Texas) where interest in SWRO desalination has been highest. Due to the more extensive international experience with SWRO desalination, information was also obtained from the countries of Australia, Israel, and Spain – all countries of significant recent large-scale SWRO desalination projects. Case studies of 11 SWRO plants and analysis of regulatory systems and permitting processes supported detailed definition of the decision-making process to set discharge permit limits, as well as defining environmental and other regulatory issues associated with concentrate regulation.
Database Of Permitting Practices For Seawater Desalination Concentrate
Abstract:
The purpose of this research project was to identify the discharge information that permitting agencies need and the decision-making process they go through to permit discharge methods in order to help desalination project proponents focus and expedite their permitting efforts.
The project documented seawater reverse osmosis (SWRO) discharge regulatory issues and provided a critical overview of facility discharge-related information required for permitting desalination projects in the United States and selected countries with advanced environmental regulations and experience in implementing seawater desalination projects. Information was gathered from the three key U.S. states (California, Florida, Texas) where interest in SWRO desalination has been highest. Due to the more extensive international experience with SWRO desalination, information was also obtained from the countries of Australia, Israel, and Spain – all countries of significant recent large-scale SWRO desalination projects. Case studies of 11 SWRO plants and analysis of regulatory systems and permitting processes supported detailed definition of the decision-making process to set discharge permit limits, as well as defining environmental and other regulatory issues associated with concentrate regulation.
Concentrating Solar Power For Seawater Desalination
Introduction:
The general perception of “solar desalination” today comprises only small scale technologies for decentralized water supply in remote places, which may be quite important for the development of rural areas, but do not address the increasing water deficits of the quickly growing urban centers of demand. Conventional large scale desalination is perceived as expensive, energy consuming and limited to rich countries like those of the Arabian Gulf, especially in view of the quickly escalating cost of fossil fuels like oil, natural gas and coal. The environmental impacts of large scale desalination due to airborne emissions of pollutants from energy consumption and to the discharge of brine and chemical additives to the sea are increasingly considered as critical. For those reasons, most contemporary strategies against a “Global Water Crisis” consider seawater desalination only as a marginal element of supply. The focus of most recommendations lies on more efficient use of water, better accountability, re-use of waste water, enhanced distribution and advanced irrigation systems. To this adds the recommendation to reduce agriculture and rather import food from other places. On the other hand, most sources that do recommend seawater desalination as part of a solution to the water crisis usually propose nuclear fission and fusion as indispensable option.
Concentrating Solar Power For Seawater Desalination
Introduction:
The general perception of “solar desalination” today comprises only small scale technologies for decentralized water supply in remote places, which may be quite important for the development of rural areas, but do not address the increasing water deficits of the quickly growing urban centers of demand. Conventional large scale desalination is perceived as expensive, energy consuming and limited to rich countries like those of the Arabian Gulf, especially in view of the quickly escalating cost of fossil fuels like oil, natural gas and coal. The environmental impacts of large scale desalination due to airborne emissions of pollutants from energy consumption and to the discharge of brine and chemical additives to the sea are increasingly considered as critical. For those reasons, most contemporary strategies against a “Global Water Crisis” consider seawater desalination only as a marginal element of supply. The focus of most recommendations lies on more efficient use of water, better accountability, re-use of waste water, enhanced distribution and advanced irrigation systems. To this adds the recommendation to reduce agriculture and rather import food from other places. On the other hand, most sources that do recommend seawater desalination as part of a solution to the water crisis usually propose nuclear fission and fusion as indispensable option.
Cleaning Your RO
Eventually the day comes when your RO system will require cleaning. Cleaning is recommended when your RO shows evidence of fouling, just prior to a long term shutdown, or as a matter of scheduled routine maintenance. Fouling characteristics that signal you need to clean are a 10-15% decrease in normalized permeate flow, a 10-15% decrease in normalized permeate quality, or a 10-15% increase in normalized pressure drop as measured between the feed and concentrate headers
Cleaning Your RO
Eventually the day comes when your RO system will require cleaning. Cleaning is recommended when your RO shows evidence of fouling, just prior to a long term shutdown, or as a matter of scheduled routine maintenance. Fouling characteristics that signal you need to clean are a 10-15% decrease in normalized permeate flow, a 10-15% decrease in normalized permeate quality, or a 10-15% increase in normalized pressure drop as measured between the feed and concentrate headers
Cleaning Procedures for Composite Polyamide RO Membrane Elements
Note: The Composite Polyamide type of RO membrane elements may not be
exposed to chlorinated water under any circumstances. Any such exposure may
cause irreparable damage to the membrane. Absolute care must be taken
following any disinfection of piping or equipment or the preparation of cleaning or
storage solutions to ensure that no trace of chlorine is present in the feedwater to
the RO membrane elements. If there is any doubt about the presence of chlorine,
perform chemical testing. Neutralize any chlorine residual with a sodium bisulfite
solution, and ensure adequate mixing and contact time to accomplish complete
dechlorination. Dosing rate is 1.8 to 3.0 ppm sodium bisulfite per 1.0 ppm of free
chlorine
Cleaning Procedures for Composite Polyamide RO Membrane Elements
Note: The Composite Polyamide type of RO membrane elements may not be
exposed to chlorinated water under any circumstances. Any such exposure may
cause irreparable damage to the membrane. Absolute care must be taken
following any disinfection of piping or equipment or the preparation of cleaning or
storage solutions to ensure that no trace of chlorine is present in the feedwater to
the RO membrane elements. If there is any doubt about the presence of chlorine,
perform chemical testing. Neutralize any chlorine residual with a sodium bisulfite
solution, and ensure adequate mixing and contact time to accomplish complete
dechlorination. Dosing rate is 1.8 to 3.0 ppm sodium bisulfite per 1.0 ppm of free
chlorine
Chemical Cleaning Effects On Properties And Separation Efciency Of An RO Membrane
Abstract: This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis
membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a
chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3
and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water
permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and
feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the
charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that
membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its
impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent
may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation
and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by
applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron
and sodium rejections are irreversible in most cases
Chemical Cleaning Effects On Properties And Separation Efciency Of An RO Membrane
Abstract: This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis
membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a
chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3
and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water
permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and
feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the
charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that
membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its
impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent
may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation
and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by
applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron
and sodium rejections are irreversible in most cases
California Desalination Planning Handbook
Introduction:
Desalination is receiving increased attention as a means for addressing the water supply challenges of California. Growing population, much of which is located in semi-arid regions of the state, and various other water demands pose increased pressure on existing water supplies. Much of California’s water supply depends on snow accumulation in the winter, providing spring runoff that flls reservoirs and replenishes often depleted groundwater supplies. But in periods of drought, water supply shortages can be encountered throughout the state, particularly in the central valley and southern portion of the state. All indications suggest the impacts of global warming will include a change in the timing of runoff and less snowfall. This will put more pressure on existing supplies, and exacerbate the impacts of drought. As the implications of global warming become clearer, more emphasis will likely be given to developing
new sources of water supply to meet existing and projected demand. While conservation and recycling are recommended as the frst course of action, other alternatives (such as desalination and increased surface and groundwater storage) are receiving increased attention.
California Desalination Planning Handbook
Introduction:
Desalination is receiving increased attention as a means for addressing the water supply challenges of California. Growing population, much of which is located in semi-arid regions of the state, and various other water demands pose increased pressure on existing water supplies. Much of California’s water supply depends on snow accumulation in the winter, providing spring runoff that flls reservoirs and replenishes often depleted groundwater supplies. But in periods of drought, water supply shortages can be encountered throughout the state, particularly in the central valley and southern portion of the state. All indications suggest the impacts of global warming will include a change in the timing of runoff and less snowfall. This will put more pressure on existing supplies, and exacerbate the impacts of drought. As the implications of global warming become clearer, more emphasis will likely be given to developing
new sources of water supply to meet existing and projected demand. While conservation and recycling are recommended as the frst course of action, other alternatives (such as desalination and increased surface and groundwater storage) are receiving increased attention.